Women with O blood type may struggle to conceive

Women with blood type 'O' could have more trouble conceiving as they age, a
study has indicated.

Researchers who tested a group of women seeking fertility treatment found those with the blood type O appeared to have a lower egg count and poorer egg quality than othersPhoto: ALAMY

By Stephen Adams, Medical Correspondent, in Denver

7:30AM BST 25 Oct 2010

Scientists have discovered for the first time that a woman's blood group could influence her chances of getting pregnant.

Researchers who tested a group of women seeking fertility treatment found those with the blood type O appeared to have a lower egg count and poorer egg quality than others.

By contrast those with blood type A seemed to have more and better quality eggs.

The findings could lead to women with type O blood being advised to try for a baby earlier, but experts said much more research was needed before such a step was taken.

O and A are the two most common blood groups in the British population: some 44 per cent are type O and 42 per cent are type A.

The study of 560 women, whose average age was just under 35, found that those with blood type O were more likely to have higher levels of 'follicle stimulating hormone' (FSH) than those with type A.

Fertility experts regard a high FSH level as a key indicator of having a low egg count, which is known as "diminished ovarian reserve".

FSH is naturally produced by the body to stimulate the follicles in the ovaries which produce eggs.

As a woman's ovaries run out of eggs in her 30s and 40s, production is stepped up to encourage more follicles to be made.

The study found that women who were blood type O were twice as likely to have an FSH level above 10 - commonly regarded as the threshold between normal and raised levels - as those in any other blood group.

It did not quantify how much more difficult women with blood type O could find it to conceive.

People with blood group A carry the A antigen, which is a protein on the surface of the cell, but this is absent in people with O type.

The lead author, Dr Edward Nejat of the department of obstetrics and gynaecology at the Albert Einstein College of Medicine in New York, said this was the first time a potential link between blood type and fertility had been identified.

He is presenting his findings, based on women undergoing fertility treatment at the Yale University IVF programme and the Montefiore Institute in New York, at the annual American Society for Reproductive Medicine (ASRM) conference in Denver on Tuesday.

He said: "Those with blood type O were twice as likely to have an FSH level over 10 than those with blood types other than O.

"We found that women with the A blood group gene were protected from this effect of diminished ovarian reserve.

"Patients with blood type O seeking infertility evaluation at these centres have a higher likelihood to be diagnosed with elevated FSH and hence manifest diminished ovarian reserve."

Susan Seenan, of Infertility Network UK, welcomed the study.

"Anything which might help couples avoid having to have fertility treatment has got to be good news," she said.

"If couples know that there is a possibility that they might have a fertility problem then perhaps they can address that earlier."

However, she cautioned that it was "early days" for the research and said more studies should be done before advising blood group O women to try for a baby earlier.

Tony Rutherford, chairman of the British Fertility Society, described the research as "interesting" in that it showed "a potential link" between blood type and fertility.

But he too said a larger study needed to be carried out among the general population - not just those who had gone for help with fertility problems.

"We need to look at a prospective group of women to see if blood group affects your chance of getting pregnant," he said.

He also said the link between blood group and other hormones that were better predictors of fertility needed to be examined.

Age is the most important determinant of ovarian reserve, which tends to start dropping in the early 30s and then accelerate in the late 30s and 40s. Being obese is also known to affect the number and quality of eggs.